mashed potato
noun /ˌmæʃt pəˈteɪtəʊ/
  /ˌmæʃt pəˈteɪtəʊ/
(also mash)
 [uncountable] (both especially British English) (also mashed potatoes [plural] British and North American English)
- potatoes that have been boiled and made into a soft mass, often mixed with butter and milk